Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!

Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.

Even though I have gotten quite good at rebuilding the 5 speed transmission (glass) box lately, the process was getting VERY old. To make matters worse, I’m not even running that much power… maybe 270 – 280 whp. While not abusive, I will admit that I drive my WRX harder than your average driver. I do both track days and the occasional trip to the 1320. Strangely enough, I’ve done more damage at the open track days than the drag strip (read: two fried front ring and pinion… thank you synchromesh!!! )

Anyway, I explored all the popular transmission options. RA Ver.6 gear sets, Kaaz / PPG gears and a 6 speeds. I kept coming back to the 6 speed STi swap. The RA gear set personally did not convince me that it was any stronger than a stock gear seat. In fact, after a quick search, I found just as many “Help, I broke my RA gear set” posts as I did with stock gears. Next was the Kaaz / PPG gears. What gives, are these gears made out of diamond incrusted platinum? The price sure reflects that. Also, I wasn’t crazy about going with a straight cut gear in a daily driver.

Finding all the right parts:
This brought me to the 6 speed. Everything about the 6 speed was better. Better ratios, better design, better (wider) gears, etc… However, the price estimates were VERY overwhelming at first. Most quotes came in around $5000 for a complete swap. Confident I could “do it myself” cheaper, I set out on Ebay to find a used STi 6 speed transmission. It took a while of searching and sniping, but I eventually found a 10,000 mile STi transmission out of a burned car for $2500.

Old 5 speed next to new 6 speed:

The next step was to determine what differential to use. Eventually, I would like to upgrade to at least an R180, but the money wasn’t in the budget. The decision was made to swap in a 3.9 ring and pinion into the stock R160 rear end.

After calling a few local junk yards, I suddenly realized how difficult Subaru junked parts are to find in the “Motor City”. Dan Ponce of Godspeed / The Tuning Factory however hooked me up big time. For $300, he simply sold me one of his “off the shelf” R160’s he had ready for his own 6 speed conversions. Score!

While differentials were seemingly hard to come by, the driveshaft was easy to find. I located a 2002 Impreza Outback with and Automatic transmission and bought the driveshaft for $50. Yes, I will probably need to upgrade to a one piece driveshaft in the near future, but my goal at this point was to simply get back on the road.

Next step in the process was to find a trans mount and shifter assembly. The trans mount was an easy find on Ebay. Also, with the new release of Subaru’s factory short throw shifter for the STi, there is a plethora of standard throw STi shifters for next to nothing. Special thanks to forum member “STi-Man” for sending me his old shifter at a great price.

All parts accounted for (or so I thought), time to start swapping:
The first step was to obviously remove the transmission. Having already done this operation five times, I created a helpful little “check list” that helps prevent me from forgetting anything:

Fortunately for me, my 6 speed transmission came out of an early 2004 model STi that already has the stub axels poking out the side of the transmission. Because of this, I was able to reuse my stock 2004 WRX front axels. I was also able to reuse my Excedy clutch, pressure plate, needle bearing and throw out bearing that was originally installed for my 5 speed. Essentially, this was a “bolt in” swap!

After a little finagling, the transmission finally seated perfectly against the little EJ205 block. Tip: with the transmission in any gear (preferably first) slide the rear driveshaft into the transmission and slowly rotate the driveshaft as you are pushing the transmission forward. This will help the input shaft splines on the transmission line up with the clutch plate.

With the trans in place, it was time to install the new STi shifter assembly. Again, another bolt in swap! The shifter boot inside the car needed to be separated from the shift knob, but this was easily (and carefully!) done with a small screwdriver. Also, having just blown $2500 on a new transmission, I was trying to reuse AS MUCH as possible. Because of this, I was actually able to reuse the stock 5 speed shift knob after trimming the white plastic from the bottom and throwing some miscellaneous spacers into the threaded hole of the knob. The final result was surprisingly nice. Personally, I like to have the shifter as close to the steering wheel as possible so I don’t mind the extra height of the 5 speed knob. Also, it helps add to the “sleeper” look:

After the shifter was done, the cross member / sub frame was bolted back into place and the new transmission was firmly secured in her new home. Swapping the rear differential was next. This job was a little more involved than originally planned simply because the rear suspension needs to be almost completely unbolted to get the rear axels out of the differential. Nothing was difficult, it just consumed more time than I had originally thought.

Now that the new 3.9 ratio rear differential was in place, all that was left was a few misc. odds and ends (driveshaft, starter, CLUTCH FORK, intercooler, etc…)

The First Drive:
My initial impression as I backed it down the driveway was: “Holy crap… when did my clutch pedal get so heavy???” I also noticed the clutch had a minor “chatter” to her. About 50 feet down my street I gave the girl a little gas and watched the tach peg to 7200 RPM while the speedometer (and acceleration for that matter) remained constant. Yup, the clutch was slipping faster than George W’s popularity.

What Went Wrong?
In the process of reinstalling the clutch slave cylinder, I noticed that the cylinder was having a much more difficult time seating against the clutch fork. I eventually got it in place, but there was obviously too much pre-load being put on the clutch fork. Even at rest, the extra pre-load had already partially disengaged the clutch. I made a phone call to Dan (again at Godspeed / Tuning Factory) and asked what he does about this problem. His response was priceless:

”There isn’t a problem… assuming you use the 6 speed clutch fork. You did use the 6 speed clutch fork right? …RIGHT? (*sigh*) I’ve got an extra one in my work bench somewhere, come by this evening and pick it up.”

Thanks again Dan.

The Second Drive:
After pulling the trans away from the engine and installing the CORRECT clutch fork (from a 6 speed transmission), the clutch pedal effort was back to normal. Also back to normal was the increased holding force of the Excedy Organic clutch!

What can I say, I love this transmission. Yes, there is an extra gear shift between zero to sixty and quarter mile runs… but who cares, I’VE GOT SIX SPEEDS NOW!!! The shorter second gear is going to be really nice on tighter road courses or roads like Tail of the Dragon. With the old 5 speed, there were a lot of tight corners that bogged down second gear but were still too fast for a full downshift into first gear. Second gear on the 6 speed is almost like a first and half gear from the old 5 speed.

So… how much did it really cost?
My original budget was $3000. I came in a whopping $43 over budget for a grand total of $3043. Here is a break down on the associated costs:

Transmission:
$2500

3.9 Ratio Differential:
$300

Automatic Transmission Driveshaft:
$50

STi OEM Shifter Linkage:
$40

Transmission Mount:
$70

Misc. brackets from dealership:
$30

Clutch Fork from 6 speed:
$50

Would I do it again?
Absolutely, this was no more difficult than replacing a stock 5 speed transmission. Obviously, the most difficult task is actually finding a reasonably priced transmission. I had to wait a few weeks to find one, but they do become available. It also helps to have cash ready for the transaction.

One more thing I forgot to add,
I was able to make my own DCCD controller out of spare parts I had laying around the lab. Basically, I reprogrammed an 8 bit microprocessor to read an analog input (potentiometer) and spit out a 150Hz square wave that varies the duty cycle between 0% and 100% (based on potentiometer voltage).

[monstergarage]FREEBIE!!!
[/monstergarage]

The little motor on the bottom was there only to simulate the solenoid during development. It will be replaced with the actual solenoid once I wire it up in the vehicle.

Very nice writeup, man! I'm doing the same thing, but I have a V8 JDM STi Spec C DCCD 6speed /w lines for external fluid cooler. My price is up around $4500 right now, but I need to sell some of the stock parts to make up for about $600 of it.

I'm currently about 90% done with my 6speed swap. Everything short of the rear differential is complete.

I purchased a 3.90 r160 from a 98 impreza off of here, but aparentely the non LSD diff's don't work with my wrx's half shafts. So I purchased a 3.90 R&P set for my stock diff and I'm having it swapped in today, so with any luck I'll have the car back by tonight or saturday.

I think that I'm going to get the Neetronics dccd controller this winter.

Awesome write-up and good job on your swap. I love my 6-speed, its perfect for autocrossing and the Dragon. I actually just stuck it in third for the whole of the Dragon. I think i only had to shift a few times. Congratulations and enjoy.

Oh and umm....why is there a raging lava flow on the drivers side of your car here?

Oh and umm....why is there a raging lava flow on the drivers side of your car here?

Back when I was 16 years old a construction crew came by to fix a pot hole infront of the house I was living in. That night, the wind picked up and blew the sign into our front yard. I put the construction sign next to the road hoping the (now gone) construction crew would see it and pick it up. Two months later, said construction crew never came back to pick up their forgotten sign.

Fast forward to spring of 2003: I'm working in the garage of my new house when the local police drives by and spots this 12 year old family heirloom sitting next to me. He gets out and reads me the riot act about how I "stole" government property. I informed this officer that:

a) Most (if not all) construction jobs are contracted out to the lowest bidder, therefore making the sign property of said bidder... if he even owned it at all. Most places rent these signs.

b) The contractor in question had abandoned this alleged stolen piece of propery some twelve years ago. If they wanted it back after twelve years, I would be more than happy to oblige.

He went on his way and the "Road Construction Ahead" sign still takes residence next to the WRX.

Bayley: I have one question for you. Did your 6speed come with somthing to mount the downpipe bracket to? My JDM tranny has nowhere that I could see to mount the stock bracket. Right now when ever I go over a decent sized bump the downpipe will knock into the transmission crossmember and it's driving me crazy!

I took a different route the first time I did a six speed into my Stage4 WRX. I bought a JDM ver8 engine/tranny/strut/brake setup and then parted everything out except the tranny and clutch. If I ignore my labor value, I almost got away with a zero net cost. Until the rear diff part spun out of control and ended up cost 1500 for a stupid R160 3.90.

And if you search on my name, you'll see where I built my own DCCD controller that works for about 140 bucks.

"Fortunately for me, my 6 speed transmission came out of an early 2004 model STi that already has the stub axels poking out the side of the transmission. Because of this, I was able to reuse my stock 2004 WRX front axels. I was also able to reuse my Excedy clutch, pressure plate, needle bearing and throw out bearing that was originally installed for my 5 speed. Essentially, this was a “bolt in” swap! "

so...if you were to use say an 05 or 06 6 speed box how would it be different? What are these "stub axles" poking out and how do you get the 05 or 06 diffy's to mount up?
I'm thinking of taking the plunge at the expense of having this money in savings.

Bayley: I have one question for you. Did your 6speed come with somthing to mount the downpipe bracket to? My JDM tranny has nowhere that I could see to mount the stock bracket. Right now when ever I go over a decent sized bump the downpipe will knock into the transmission crossmember and it's driving me crazy!

No, my transmission did not come with an exhaust hanger either. I was able to "modify" the old hanger from the 5 speed, but so far I haven't needed to use it. I'm running a catless downpipe with the Blitz Nur-Spec (Touring) R and nothing hits or rubs.

were you running full synchromesh in the transmission, or a cocktail? I'm curious.

2 quarts synchromesh and 2 quarts synthetic 75W.

I've played around with quite a few gear oils and regular gear oil (i.e. non-synthetic) has been the only oil that has really held up. Full synthetic is too hard on the synchro's and synchromesh simply can't withstand the heat from the front ring and pinion.

"Fortunately for me, my 6 speed transmission came out of an early 2004 model STi that already has the stub axels poking out the side of the transmission. Because of this, I was able to reuse my stock 2004 WRX front axels. I was also able to reuse my Excedy clutch, pressure plate, needle bearing and throw out bearing that was originally installed for my 5 speed. Essentially, this was a “bolt in” swap! "

so...if you were to use say an 05 or 06 6 speed box how would it be different? What are these "stub axles" poking out and how do you get the 05 or 06 diffy's to mount up?
I'm thinking of taking the plunge at the expense of having this money in savings.

You would need the correct style axles. They have the stub axle on the axle side of the CV joint and slip into the holes in the transmission (like the rear diff and axles). I've had both types in my WRX, and they bolt in with no problem. You can even re-use the WRX hubs if you want.